Life fundamentals

The three rules of Conway's Game of Life, and a glossary of every term a newcomer will hit: still life, oscillator, period, spaceship, glider, gun, puffer, soup, stabilisation.

The rules

Conway's Game of Life runs on a grid of cells, each alive or dead. Every generation, every cell updates at once, according to how many of its 8 neighbours (including diagonals) are alive right now:

2 or 3 live neighbours, and the cell is alive: it survives.
Exactly 3 live neighbours, and the cell is dead: it's born.
Anything else: the cell is dead next generation (too few neighbours to sustain it, or too many).

This ruleset has a name — B3/S23 ("birth on 3, survival on 2 or 3") — and it's the one every implementation calling itself "Conway's Game of Life" uses, AFTERLIFE included. There is no player once a starting pattern is set; the rule is entirely deterministic, so the same start always produces the same future. See it running on a real glider on the guide's landing page.

Glossary

Terms you'll hit throughout the app and this wiki, in the order a newcomer tends to meet them.

soup: A starting arrangement with no particular design — cells placed at random or by hand with no plan for what they’ll become. Most soups die out or settle into a scattering of still lifes and oscillators.
still life: A pattern that does not change at all from one generation to the next — every live cell has exactly 2 or 3 live neighbours, and every dead neighbour has anything other than exactly 3. The block, beehive and boat are the smallest examples.
oscillator: A pattern that returns to its exact starting shape after a fixed number of generations, then repeats forever. See period.
period: How many generations an oscillator (or spaceship) takes to return to its original shape (in a spaceship’s case, the same shape in a new position). A blinker has period 2; the pentadecathlon has period 15.
spaceship: A pattern that reproduces its own shape, translated to a new position, after a fixed period — it travels indefinitely. The glider is the smallest; LWSS/MWSS/HWSS are the classic orthogonal ships.
glider: The smallest known spaceship: 5 cells, period 4, moving one cell diagonally every period. See it animated on the guide’s landing page.
gun: A pattern that periodically emits a spaceship (usually a glider) without being consumed itself, growing the population forever. The Gosper glider gun — the first gun ever discovered — fires one glider every 30 generations.
puffer: A pattern that moves like a spaceship while leaving a trail of stable or periodic debris behind it, like exhaust. AFTERLIFE deliberately ships none: see why, in Verification.
methuselah: A small, unremarkable-looking pattern that takes an unusually long time to stabilise, often after growing much larger first. The R-pentomino (5 cells, 1103 generations) and acorn (7 cells, 5206 generations) are the catalogue’s two extreme examples.
stabilisation: The point after which a pattern’s population and behaviour settle into either a fixed still life, a repeating oscillation, or total extinction — it stops doing anything new.
toroidal / torus: The shape of AFTERLIFE’s world: the grid’s edges wrap around, top to bottom and left to right, like the surface of a doughnut. A glider that exits the right edge re-enters on the left. See How it works.